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Effect of Surface Stoichiometry on Blinking and Hole Trapping Dynamics in CdSe Nanocrystals

Journal Article · · Journal of Physical Chemistry. C
 [1];  [2];  [2];  [3]
  1. Brookhaven National Lab. (BNL), Upton, NY (United States); Columbia Univ., New York, NY (United States)
  2. Columbia Univ., New York, NY (United States)
  3. Brookhaven National Lab. (BNL), Upton, NY (United States)
Here, we measure the photoinduced carrier dynamics as the surface composition of CdSe nanocrystals is systematically varied from metal rich (~80% surface Cd) to nearly stoichiometric (~50% surface Cd). Using time-resolved optical spectroscopy, we determine that the luminescence lifetime is controlled by the rate of hole trapping at the newly exposed surface selenium atoms. However, the increased rate of the photoluminescence decay is not sufficient to explain the decreased photoluminescence quantum yield, and requires a growing proportion of nanocrystals in a dark or “OFF” state to explain the data. A global kinetic model is proposed that relates the fraction of selenium sites to the rate of hole trapping. A linear relationship between the rate of hole trapping and the fraction of exposed Se sites (xSe) is observed within the range of accessible stoichiometries (xSe = 0.5–0.2). Extrapolation to higher surface cadmium fractions suggests that not all Se sites serve as effective hole traps. These findings confirm the strong nonlinear dependence of the fluorescence yield on the nanocrystal stoichiometry.
Research Organization:
Energy Frontier Research Centers (EFRC) (United States). Re-Defining Photovoltaic Efficiency Through Molecule Scale Control (RPEMSC)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Grant/Contract Number:
SC0001085; SC0006410; SC0012704
OSTI ID:
1370370
Journal Information:
Journal of Physical Chemistry. C, Journal Name: Journal of Physical Chemistry. C Journal Issue: 49 Vol. 119; ISSN 1932-7447
Publisher:
American Chemical SocietyCopyright Statement
Country of Publication:
United States
Language:
English

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Cited By (8)

Excited-State Dynamics in Colloidal Semiconductor Nanocrystals journal August 2016
Origin of Improved Photoelectrochemical Water Splitting in Mixed Perovskite Oxides journal September 2018
An Ultrafast Transient Absorption Study of Charge Separation and Recombination Dynamics in CdSe QDs and Methyl Viologen: Dependence on Surface Stoichiometry journal March 2018
Excited-State Dynamics in Colloidal Semiconductor Nanocrystals book August 2016
From ligands to binding motifs and beyond; the enhanced versatility of nanocrystal surfaces journal January 2016
Surface stoichiometry manipulation enhances solar hydrogen evolution of CdSe quantum dots journal January 2018
Real colloidal quantum dot structures revealed by high resolution analytical electron microscopy journal October 2019
Origin of Improved Photoelectrochemical Water Splitting in Mixed Perovskite Oxides text January 2018

Figures / Tables (7)


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